Definition of Know-nothing

The Know Nothing was a movement by the nativist American political faction of the 1850s, characterized by political xenophobia, anti-Catholic sentiment, and occasional bouts of violence against the groups the nativists targeted. It was empowered by popular fears that the country was being overwhelmed by German and Irish Catholic immigrants, who were often regarded as hostile to republican values and controlled by the Pope in Rome. Mainly active from 1854 to 1856, it strove to curb immigration and naturalization, though its efforts met with little success. Membership was limited to Protestant males of British American lineage. There were few prominent leaders, and the largely middle-class and entirely Protestant membership fragmented over the issue of slavery.